Effect of crown margins on periodontal conditions in regularly attending patients

Effect of crown margins on periodontal regularly attending patients

conditions

in

James D. Bader, D.D.S., M.P.H.,* R. Gary Rozier, D.D.S., M.P.H.,** Walter T. McFall, Jr., D.D.S., M.S.,*** and Diane L. Ramsey**** University

of North

Carolina,

School of Dentistry,

Chapel Hill, N.C.

Subgingival margins of cast restorations have been associated with increased gingival inflammation and probing depth, but it is not known if such effects would be seen among patients receiving regular professional care. In this study, 831 regularly attending patients in 36 North Carolina dental practices were examined. Plaque, gingival inflammation, calculus, and probing depth were assessed on facial and mesiofacial surfaces of the Ramfjord teeth. Surface-specific analyses showed significantly greater (p < 0.06) gingival inflammation and deeper probing depths with subgingival cast restoration margins for nearly all surfaces examined. Less frequently, decreases in plaque and calculus were associated with the presence of crowns. Intact surfaces in patients with cast restorations were not significantly different from the same surfaces in patients without cast restorations. Even among patients receiving regular preventive dental care, subgingival margins are associated with unfavorable periodontal reactions. (J PROSTHET DENT 1991;66:75-9.)

F

or more than three decades, attention has been paid in the research literature to the local effects of cast restorations on periodontal conditions in animals1-3 and humans.4-‘3 The nearly unanimous conclusion reached by these studies has been that margins of cast restorations placed at or below the gingival margin will cause some increase in gingival inflammation and probing depth. Meticulous oral hygiene seemsto mitigate these effects only when margins are not subgingival. A careful consideration of the circumstances of these studies suggests that such a conclusion may not be easily generalizable to dental patients who receive regular care in private practices. With a single exception, l2 all of the human studies have been performed among dental school patient populations, with restorations placed by students and faculty. In at least four studies, these patients were receiving complex periodontal treatment.5p g-11$ l3 The extent to which the results can be generalized to the larger population of regular users of dental services is unknown in the light of possible differences in the design and execution of the castings, the patients’ demographic characteristics and disease experi-

Supported by National Institute for Dental Research grant No. ROl DE07718. Presented at the International Association for Dental Research, Dublin, Ireland. *Research Associate Professor, Department of Dental Ecology.

**AssociateProfessor,Department of Health Policy and Administration, School of Public Health. ***Professor, Department of Periodontics.

****Social ResearchAssist+.mt,Department of Dental Ecology. 10/l/22251

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ence, and the posttreatment recall and maintenance regimens. The presence of multiple crowns and fixed partial dentures usually described in these studies may reflect a basic difference in attention to and resultant levels of oral health among the patients examined. The extent to which recipients of crowns may be different from other patients is essentially unexplored, and it is possible that untoward effects of crowns are overestimated in these studies due to lower general levels of oral health. Some study design features are problematic, such as assessments based only on facial or lingual surfaces,4v7,* the assumption of independence of multiple surfaces for the same toothl”~ l2 or teeth for the individual 4-6ls-l3 and the lack of controls for comparisons across specific tooth type.5T6 g-13 Even with these shortcomings, it is unlikely that the basic conclusion, that “margins of cast restorations placed at or below the gingival margin have periodontal effects,” can be challenged. The preponderance of subgingival margins suggests that practitioners have not identified substantial deleterious effects or that they believe the esthetic demands outweigh concern over such effects, and they have continued the practice of placing margins subgingivally despite longstanding recommendations against it>* I4 These effects may be minimized because these patients are regular recipients of the treatment efforts of the practice. More information concerning the periodontal effects of subgingival margins among regularly attending dental patients is necessary before current procedures can either be supported or discouraged. This article reports the results of an analysis of periodontal conditions among 831 regularly attending patients with cast restorations in 35 private dental practices.

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Table I. Overall distributions

ET AL

of index scores and score means, by crown status (n = 9124 surfaces) Index 0

Plaque index* Crowned surfaces Uncrowned surfaces Calculus index* Crowned surfaces Uncrowned surfaces Gingival inflammation index* Crowned surfaces Uncrowned surfaces

Score mean

1

2

3

83.4 %

13.3%

71.7%

17.5%

3.3% 4.6%

0.0% 0.2%

0.20 0.27

96.1% 89.5%

2.9% 8.1%

1.0%

N/A N/A

0.05

2.3% 12.3% 4.7%

0.2% 0.1%

0.49 0.22

64.1% 83.0% O-l mm

Probing depth measurements* Crowned surfaces Uncrowned surfaces

score?

23.5% 12.2% 2-3

mm

4-5

0.13

6+

mm

44.9%

54.1%

0.9%

0.1%

1.62mm

63.3%

36.1%

0.5%

0.1%

1.34 mm

‘Crowned and uncrowned distributions significantly different, x2, p < 0.01. tIndex scores of 1 indicate: plaque visible with aid of explorer; supragingival calculus; gingival redness and swelling. Scores of 2 indicate: discontinuous band of visible plaque; subgingival calculus, gingival bleeding upon probing. Scores of 3 indicate: heavy coating of plaque; spontaneous gingival bleeding.

METHODS The practices from which the patient data were collected were those that had enrolled as volunteer participants in a long-term study of the effectiveness of continuing dental education. These practices represented two thirds of all eligible practices (full-time general practices in existence more than 3 years) in two North Carolina counties. A random start, sequential selection process was used to identify the records of 80 adult patients in each practice with a 5year history of regular visits.15 Requests for participation were made among this pool of patients until 32 had been scheduled for an oral examination in the practitioner’s office.16 During this examination, the patient’s participation in additional annual examinations was requested. The analyses reported here are based on the results of the second annual examination, and include patients from 35 of the original 36 practices. Of 1058 patients examined initially in these practices, 831 returned for the second examination. The oral examination focused exclusively on periodontal conditions. Indices included: the plaque index (PlI),” the gingival inflammation index (GI),l* a calculus index (CI),” and measures of probing depth (PD) and gingival recession.20 These measurements were applied to the facial and mesiofacial surfaces of the Ramfjord teeth or acceptable substitutes. 2o Presence of cast restorations was noted during the examination. The relationship of cast restoration margins to the gingival margin was determined through the gingival recession measurement, which used the restoration margin, when present, as the reference point. An initial set of analyses compared the distribution of

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scores for each index across all surfaces grouped by the presence or absence of a cast restoration margin. A second analysis for each index was performed separately for each of the 12 sites. This approach controls any site/crown status interaction, for example, the possibility that sites more likely to have periodontal disease will also be more likely to have a crown, This approach assumes that periodontal conditions of uncrowned surfaces in subjects with one or more crowns are not different from conditions among patients without any crowns. This premise was tested in a separate series of individual surface analyses. The initial analyses used the raw index scores for the PlI, GI, CI, and PD categories of 0 to 1 mm, 2 to 3 mm, 4 to 5 mm, and 6+ mm. The chi square statistic was used to test for statistically significant differences between crowned and uncrowned surfaces. For all subsequent analyses of individual surfaces, PlI, GI, and CI scores were collapsed into 0 (absent) and 1 (present) categories, while PD categories of 0 to 1 mm and 2+ mm were compared. Because each patient is represented by a single observation in each surfacespecific analysis, it was possible to control for the effects of patient sex, race, and age group (less than 40,41 to 60,61+) by using the Cochran-Mantel-Haenszel general association statistic for testing differences between the crown status groups.21*22

RESULTS Among the 831 patients, 4562 index teeth were available for scoring. Of these teeth, 599 (13 % ) in 367 patients (44 % ) had a cast restoration. The proportion of each index tooth with a cast restoration was: No. 3,18 % ; No. 9,10 % ; No. 12, 16% ; No. 19, 30% ; No. 25, 2% ; and No. 28, 6%. Restora-

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Table II. Proportion of plaque index scores greater than 0 by crown margin status Tooth No. 3

Fat

Surface

Surface

Surface MC%

Mes

Fat

Mes

13

32

5

17

I

Supragingival cro’wn margin Subgingival crown margin

25 6

177

8

15

27* 5

Fat, Facial; Mes, mesiofacial. -, Ten or fewer observations. *,tSignificantly different from no crown distribution, Cochran-Mantel-Haenszel *p < 0.05, tp < 0.01.

Table III.

Surface

Fat

No crown

26

28

Surface

Surface

19

12

9

Fae

Fat

Mes

24

18

43

16

1f3*

26 12*

32t

-

Mes

Fat

Mes

43

13

40

-

10

25*

general association statistic:

Proportion of calculus index scores greater than 0 by crown margin status Tooth No. 3

9

Surface

No crown Supragingival Subgingival

crown margin crown margin

12

19

Surface

Surface

25

Surface

Surface

Mes

Fat

Me6

Fat

Mes

Fat

Mes

Fat

Mes

Fat

Mes

5 6

10 -

2

3 -

1 0

3 -

4 4

12 -

16 -

44 -

5

-

-

12 _

4

4

1

4

I*

-

-

2

9

1*

2*

tion margins were supragingival for 11% of facial surfaces and for 4% of mesiofacial surfaces. Table I shows the overall distributions for the four periodontal outcomes, as well as the mean index scores. For both plaque and calculus scores, prevalence of the condition was significantly lower for crowned surfaces. Overall, however, the prevalence of plaque and calculus was generally low and differences by crown status tended to be quite small. For gingival inflammation, the distribution of scores for crowned surfaces contained significantly greater proportions of scores indicating redness or swelling, and bleeding. For PD, a significantly greater number of crowned surfaces had measurements of 2 to 3 mm. PDs greater than 3 mm were found extremely infrequently on these index teeth. Table II shows the proportion of plaque index scores greater than 0 for each of the 12 tooth surfaces by crown status and location of crown margin. Because supragingival margins were relatively infrequent, some observations had 10 or fewer total scores. These sites were not analyzed. Scores indicating the presence of plaque were significantly less frequent on surfaces with subgingival crown margins than on uncrowned surfaces in 5 of 10 individual

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Fat

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Fat, Facial, Mea, mesiofacial. -, Ten or fewer total observations. *Significantly different from no crown distribution, Cochran-Mantel-Haenszel general association statistic: p <

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surface comparisons. Conversely, for those sites with sufficient supragingival margins to permit analyses, the presence of plaque was more frequently associated with such margins. Table III shows the results of parallel analyses for calculus index scores. In these surface-specific analyses, the prevalence of calculus was significantly lower for crowned surfaces with subgingival margins than for surfaces without crowns in 3 of 10 sites. As suggested by the distribution shown in Table I, the overall slightly greater prevalence of calculus in uncrowned surfaces was accounted for primarily by supragingival calculus (score of 1). Table IV shows the results of the analyses of gingival inflammation index scores. A strong pattern of gingival inflammation being more prevalent on all surfaces with crowns was evident. Nine of 10 comparisons were significant for subgingival margins, and two of three were significant for supragingival margins. Although not shown in the table, the increased frequency of non-zero scores was fairly evenly distributed between scores of 1 and 2 to 3. Table V shows increased PD measurements associated with crowned surfaces in 10 of 10 comparisons. The three supragingival comparisons also show more frequent deeper

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BADER

Table

ET AL

Proportion of gingival inflammation index scores greater than 0 by crown margin status

IV.

Tooth No. 3

9

Surface

12

Surface

Fat

Mes

No crown

14

Supragingival crown margin Subgingival crown margin

507 21

Surface

V.

26

Surface

Fat

Mes

Fat

Mes

21

9

16

31*

-

-

10 36*

2gt

42t

36t

Fat, Facial; Mes, mesiofacial. -, Ten or fewer total observations. *,tSignificantly different from no crown distribution, Cochran-Mantel-Haensel

Table

19

28

Surface

Fat

Mes

22

15

25

-

17

-

W

sot

407

-

Fat

Surface

Mes

Fat

Mes

18

26

29

19

-

-

-

-

-

34-t

53t

general association statistic: *p < 0.05, tp < 0.01.

Proportion of probing depth (PD) measurements greater than 1 mm by crown margin status Tooth No. 3

9

Surface

12

Surface

Surface

26

Surface

28

Surface

Surface

Fat

Mes

Fat

Mes

Fat

Mes

Fat

Mes

Fat

Mes

Fat

Mes

18 25

18 -

16 -

56 -

78 -

14 26

66 -

4 -

34 -

-

Subgingival crown margin

31t

w

3gt

80t

12 27 23*

7

crown margin

W

25t

807

-

-

27t

65 81*

No crown Supragingival

Fat, Facial; Mes, mesiofacial. -, Ten or fewer total observations. *,tSignificantly different from no crown distribution, Cochran-Mantel-Haenszel

measurements, but the differences were not statistically significant. Finally, analyses were performed that compared the uncrowned surfaces of patients with one or more crowns with the same surfaces in patients without any crowns. The proportions of these combined surfaces with plaque, gingivitis, calculus, and PDs of 2 mm or deeper form the values for the “no crown” rows in Tables II through V. No significant differences were found in any of these surface comparisons for gingival inflammation or PD measurements. For 24 comparisons, the difference in prevalence exceeded three percentage points in only four instances, with a maximum difference of eight points. The difference in prevalence of plaque was statistically significant on the mesial surfaces of teeth No. 3 and 12, where the plaque was more prevalent among patients with no crowns. These differences were small, however. For one surface (the facial surface of tooth No. 25), calculus was more prevalent among patients with no crowns, but again the differences were small.

DISCUSSION It is clear from the results of this study that the presence of a cast restoration does have an influence on local peri-

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19

general association statistic: *p < 0.05, tp < 0.01.

odontal conditions among regularly attending patients. This general observation agrees with the findings in previous reports of restoration margin effects on gingival inflammation and PD. The magnitude of the mean difference in PD between crowned and uncrowned facial and mesiofacial surfaces found in this study (0.28 mm) is within the range of mean differences of 0.10 mm to 0.53 mm reported for various surfaces of other studies. Similarly, the mean difference in the GI score of 0.27 is within the reported range of 0.25 to 0.90. With respect to plaque, previous reports have demonstrated both higher43l2 and lowers levels associated with crown margins. The lower levels found in this study may be a result of a combination of the placebo effect, wherein patients cleaned their teeth carefully prior to the examination, and the fact that plaque does not accumulate as easily on porcelain crown surfaces,8 which represented a substantial proportion of crown surfaces in this study. Calculus scores were reported in only one other study,12 and the pattern of lower prevalence for crowned surfaces was the same. These results do not duplicate earlier observations of a clear difference in periodontal effects between margins placed supragingivally and those placed at or below the

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gingival margin. Only a small proportion of the margins were supragingival, and the resultant small sample size limits the strength of the statistical analyses. Among the analyses that were (completed, the pattern for supragingival margins is suggestive of gingival inflammation scores and PD measurements equivalent to those of subgingival margins and thus is significantly worse than for uncrowned teeth. It is possible that some of these margins were originally placed subgingivally, and that the supragingival classification is a result of disease processes, which would explain elevated inflammation and PDs. Also, it has been suggested that adequacy of the margin (and presumably location) is less i,mportant than crown contours and embrasures.12

CONCLUSIONS The results of this study offer the clinician both comfort and caution. The comfort is due to the relatively small magnitude of the PD effects detected. The presence of a crown margin is ae#sociatedwith an increase in PD of 0.28 mm. Another way of expressing this difference is that approximately 20 of every 100 surfaces would be categorized as 2 to 3 mm, rather than 0 to 1 mm, which is still within the physiologically normal range. Virtually no effects involving greater l?Ds were seen. The caution stems from the increases in gingival inflammation and bleeding associated with crowns. Again, approximately 20 mo,reof every 100 surfaces will exhibit these characteristics if a crown margin is present, and here the conditions cannot be considered within the range of nornality. These patients represent the “best” patients in practices in terms of regularity of recall visits where appropriate periodontal preventive and maintenance procedures were provided. The patients with crowns do not display poorer overall oral health; the comparisons of their uncrowned teeth with the same teeth in patients with no crowns show no d:ifferences for PD and gingival inflammation, and a slight tendency for a reduced prevalence of calculus and plaque. CIinicians must be aware that cast restorations can result in deleterious periodontal effects and should emphasize appropriate preventive procedures to minimize these eRects.

2. Marcum J. The effect of crown marginal depth upon gingival tissue. J PROSTHET DEXT 1967;17:479-87. 3. Karlaen K. Gingival reactions to dental restorations. Acta Odontol Stand 1970;28:895-904. 4. Silness J. Periodontal conditions in patients treated with dental bridges. III. The relationship between the location of the crown margin and the periodontal condition. J Periodontol Res 1970;5:225-9. 5. Bergman B, Hugoson A, Olsson C. Periodontal and prosthetic considerations in patients treated with removable partial denture and artificial crowns. A longitudinal two-year study. Acts Odontol Stand 1971;29:624-38. 6. Jones J. The success rate of anterior crowns. Br Dent J 1972;132:399403. 7. Richter W. Ueno H. Relationship of crown margin placement to gingival inflammation. J PROSTHET DEB 1973;30:156-61. 8. Newcomb C. The relationship between location of subgingival crown margins and gingival inflammation. J Periodonto 1974;46:151-4. 9. Valderhaug J, Birkeland J. Periodontal conditions in patients 5 years following insertion of fixed prostheses. J Oral Rehabil 1976;3:237-43. 10. Valderhaug J, Heloe L. Oral hygiene in a group of supervised patients with fixed prostheses. J Periodonto 1977;48:221-4. 11. Nyman S, Lindhe J. A longitudinal study of combined periodontal and prosthetic treatment of patients with advanced periodontal disease. J Periodontol 1979,50:163-9. 12. Grasso J, Nalbandian J, Sanford C, Bailit H. Effect of restoration quality on periodontal health. J PROSTHET DENT 1985;53:14-9. 13. Muller H. The effect of artificial crown margins at the gin&al margin on the periodontal conditions in a group of periodontally supervised patients treated with fixed bridges. J Clin Periodontol 1986;13:97-102. 14. Loe H. Reactions of marginal periodontal tissues to restorative procedures. Int Dent J 196&l&759-78. 15. McFall W, Bader J, Roxier R, Ramsey D. Presence of periodontal data in patient records of general practitioners. J Periodontol1988;59:445-9. 16. McFall W, Bader J, Rosier R, et al. Clinical periodontal status of regularly attending patients in general dental practices. J Periodontol 1989;60:145-50. 17. Silness J, Lee H. Periodontal disease in pregnancy. II. Correlation between oral hygiene and periodontal condition. Acta Odontol Stand 1964;22:121-35. 18. Loe H, Silness J. Periodontal disease in pregnancy. I. Prevalence and severity. Acta Odontol Stand 1963;21:533-51. 19. Miller A, Brunelle J, Carlos J, et al. Oral health of United States adults. Bethesda: National Institute of Dental Research, 1987. NIH Publication No. 87.2868. 20. Ramfjord S. The periodontal disease index (PDI). J Periodontol 1967;38:602-10. 21. Landis R, Heyman E, Koch C. Average partial association in three-way contingency tables: a review and discussion of alternative tests. Int Stat Rev 1987;46:237-54. 22. SAS Institute, Inc. SAS/STAT User’s guide. 6.03 edition. Gary, NC: SAS Institute, 1988. Reprint requests to: DR. JAM= D. BADER SCHOOL OF DENTISTRY, CB #3745 UNIVERSITY OF NORTH CAROLINA CHAPEL HILL, NC 27599

Wethank Michael J. Symons for his guidance and contributions analyses.

to the

REFERENCES 1. Waerhaug J. Tissl~e reactions around artificial crowns. J. Periodonto1 1953;24:172-85.

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